import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        char[] values = sc.next().toCharArray();
        int plus = 2;
        int normal = 0;
        for (int i = values.length - 1; i >= 0; i--) {
            int nextPlus;
            int nextNormal;
            if (values[i] == '1') {
                nextPlus = Math.min(plus, normal + 1);
                nextNormal = normal + 1;
            } else {
                nextPlus = plus + 1;
                nextNormal = Math.min(plus + 1, normal);
            }
            plus = nextPlus;
            normal = nextNormal;
        }
        System.out.println(Math.min(plus + 1, normal));
    }
}

class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}